Topic: Battery Eliminator

[lessarde]

Hello all, I'm doing a cafe project and trying to get as small a battery as possible.  I've eliminated the starter so I don't need much amps up front.  A capacitor would work but I have Dyna coils and ignition and the computer chip needs some current before starting.  Has anyone ever tried a tiny battery with a capacitor?  How about 2 6v batteries in series?  What's the smallest anyone has gotten away with?  thanks a lot!

[Dennis]

Actually your alternator needs current to start also. Probably a lot more than any "computer chip" would require.

As far as your questions are concerned ......
1. Don't see where using a cap with a battery would help you
2. 2 - 6 volt batteries in series is by definition a 12 volt battery, should work fine.
3. How small? No idea but I would guess, it wouldn't take much for what you want to do as long as you don't let it idle and have the ignition and lighting running off the battery.

[TwoTired]

What bike are you working on?

[scondon]

   I was planning asking the same question and seeing as this thread is already started I'll add my query here.

      In the FAQ's there is a link for a "Battery Eliminator".  I have no idea if it would work on any of the SOHC's but someone saw fit to include it in the "Where to buy" list for our bikes. I'm building a "Frankenstein" road racer and am dropping weight from the bike wherever I can. If I could replace the battery with this I would. Bike is a '78 750 w/Accel 5.0 coils and Dyna S ignition. Kickstart only.

http://www.bat-pac.com/index.htm

[eldar]

I heard that terry in oz installed a magneto on one of his bikes. That would eliminate the need for a battery or allow the use of a VERY small battery. I know they work with lights and such. I had a yammy with a magneto and never had a battery. Lights worked fine. No electric start of course.

I say ask terry what he did. See what he did and if it is something you would like to try.

[scondon]

     I actually drove and picked up that ARD magneto for Terry so I got to see it up close and personal. Pretty interesting setup to say the least, but a bit bulky for my taste. I'm not opposed to running one but would like to keep the ignition I have if I can. I am at least familiar with the Dyna S.

[TwoTired]

   I was planning asking the same question and seeing as this thread is already started I'll add my query here.

      In the FAQ's there is a link for a "Battery Eliminator".  I have no idea if it would work on any of the SOHC's but someone saw fit to include it in the "Where to buy" list for our bikes. I'm building a "Frankenstein" road racer and am dropping weight from the bike wherever I can. If I could replace the battery with this I would. Bike is a '78 750 w/Accel 5.0 coils and Dyna S ignition. Kickstart only.

I would very much like to see the bat pac pointer in the FAQ removed, as I don't see how it can work with the SOHC4 charging system that needs the field excited to produce any power, ever.  To my knowledge not one single person has EVER posted a working solution using this device.
I'm very close to my limit of rehashing this same old topic.  I fear the value of this forum will be severely diminished if we continue with a policy of distributed misinformation.

Sean,
My recommendation is that you work up an electrical budget for the bike you wish to build, using the components you plan on incorporating.
Here's a spring board example:

Stock CB 750 electrical budget   /  minimum lighting
3.3 A  / 40 W -low beam Headlight
___________- Neutral lamp
___________- oil lamp
0.58A / 7W    -tail light
1.91A / 23W  -Stop light
1.17A / 14 W  -7W   x 2 Front run lights
1.0 A  / 12W   - 3W X 4 Instrument lights
1.2 A  / 15W  - ignition estimate  (while idling with points, 95 degree dwell on each, 5 ohm coils)
1.7A   / 20.4W – Alternator field coil (While idling)
0.0A   / 0 W - Turn sigs?
__________ - Dyna ignition module ?
9.78A  /117.4W -total  (normally drawn from system)
 0.05A /2.5W  - wiring, connector, and switch contact resistance losses
                       (Assumes 0.5 v voltage loss in wiring at 10 A draw)

approx.  3.28A (or 40 watt) delivery from alternator at idle (1000RPM), provided field coil is powered with 12V. 
Extrapolated from Honda Shop manual chart of 6.5 amp drain with lights on.

Peak Alternator output – 17.5A  (210 watts at 5000 RPM)

To run the engine, the ignition and alternator must be fully powered (1.7 + 1.2 A or 2.9 Amps) The idling alternator (without battery) can probably supply this much power.  Just don't step on the brake or operate ANY lighting.  You'll still need a power source (about 3 amps) to get the alternator and bike started with ALL lighting disabled.

Warning...There may be math errors above.

Cheers,

[eldar]

so then, lets get rid of the bat-pac but put in something on magnetos since a prominent member seems to have done it successfully. a magneto is completely pheasable.

[csendker]

Since most of the battery elimination thoughts seems to be typically associated with weight reduction {sometimes physical size too, I guess}, it will be interesting to see what the weight implications are of the magneto & dinky battery vs. standard alternator & regular battery.  Considering you need an external juice source to run these bikes below ~2K RPM, I would think the best solution, albeit more radical, would be to modify the alternator to self-exciting {eliminate the basic issue} and then go with the smallest battery for your electrical goodies rather than any battery modifications as the primary solution.  There's gotta be an answer somewhere, but the electrical design on these bikes does make it a complex problem.

And just how much do jumper cables weigh?

[scondon]

   I was planning asking the same question and seeing as this thread is already started I'll add my query here.

      In the FAQ's there is a link for a "Battery Eliminator".  I have no idea if it would work on any of the SOHC's but someone saw fit to include it in the "Where to buy" list for our bikes. I'm building a "Frankenstein" road racer and am dropping weight from the bike wherever I can. If I could replace the battery with this I would. Bike is a '78 750 w/Accel 5.0 coils and Dyna S ignition. Kickstart only.

I would very much like to see the bat pac pointer in the FAQ removed, as I don't see how it can work with the SOHC4 charging system that needs the field excited to produce any power, ever. To my knowledge not one single person has EVER posted a working solution using this device.
I'm very close to my limit of rehashing this same old topic. I fear the value of this forum will be severely diminished if we continue with a policy of distributed misinformation.

Sean,
My recommendation is that you work up an electrical budget for the bike you wish to build, using the components you plan on incorporating.
Here's a spring board example:

Stock CB 750 electrical budget / minimum lighting
3.3 A / 40 W -low beam Headlight
___________- Neutral lamp
___________- oil lamp
0.58A / 7W    -tail light
1.91A / 23W -Stop light
1.17A / 14 W -7W   x 2 Front run lights
1.0 A / 12W   - 3W X 4 Instrument lights
1.2 A / 15W - ignition estimate (while idling with points, 95 degree dwell on each, 5 ohm coils)
1.7A / 20.4W – Alternator field coil (While idling)
0.0A / 0 W - Turn sigs?
__________ - Dyna ignition module ?
9.78A /117.4W -total (normally drawn from system)
 0.05A /2.5W - wiring, connector, and switch contact resistance losses
 (Assumes 0.5 v voltage loss in wiring at 10 A draw)

approx. 3.28A (or 40 watt) delivery from alternator at idle (1000RPM), provided field coil is powered with 12V.
Extrapolated from Honda Shop manual chart of 6.5 amp drain with lights on.

Peak Alternator output – 17.5A (210 watts at 5000 RPM)

To run the engine, the ignition and alternator must be fully powered (1.7 + 1.2 A or 2.9 Amps) The idling alternator (without battery) can probably supply this much power. Just don't step on the brake or operate ANY lighting. You'll still need a power source (about 3 amps) to get the alternator and bike started with ALL lighting disabled.

Warning...There may be math errors above.

Cheers,

  Excellent,thanks TT     The "Year of the Carbs" is nearing the end and the "Year of Electronics" is about to commence. After some study and figuring out exactly what will be on the bike I shall return.

[dusterdude]

Since most of the battery elimination thoughts seems to be typically associated with weight reduction {sometimes physical size too, I guess}, it will be interesting to see what the weight implications are of the magneto & dinky battery vs. standard alternator & regular battery.  Considering you need an external juice source to run these bikes below ~2K RPM, I would think the best solution, albeit more radical, would be to modify the alternator to self-exciting {eliminate the basic issue} and then go with the smallest battery for your electrical goodies rather than any battery modifications as the primary solution.  There's gotta be an answer somewhere, but the electrical design on these bikes does make it a complex problem.

And just how much do jumper cables weigh?

is self exciting possible?

[eldar]

Well you would need to put in a comparatively sized permanent magnet. Our alts use an electro-magnet.  You could do it but I think the regulator would need to be changed too.Some rewiring would be required also. The good thing with the ard magneto terry got was that it had the wiring at least partially done.

[Dennis]

Well you would need to put in a comparatively sized permanent magnet. ..... but I think the regulator would need to be changed too.Some rewiring would be required also.

Would definitely require a different regulator and rewiring. The circuitry and regulators used for PM alternators is totally different from the type on the SOHC4 bikes.

[lessarde]

Thanks for the info.  I have tried the bat-pac and it definately does not work.  I bought a very small battery yesterday (2" x 2" x 3").  It's 12v with very low amps but it ran the the lights and so forth just fine for a couple hours yesterday.  I'm going to ride it again tonight and see.  It weights about a pound and fits very nicely under my seat.  I am using a kick starter. 

[lessarde]

Sorry, I should mention I have a 74/75 CB750 motor in a 78 frame.  It has the Dyna coils, 836 kit, high lift cam...etc. 

[fang]

Beautiful bike -- I am so glad that the cafe scene is returning!  (I am a dyed in the wool cafe head myself.)
I like that you kept the front fender. It looks nice and nostalgic with it and the rims painted black.  Very tastefully done. 

I am not certain that the discussion about removing the battery needs to be orbiting around the concept of conserving weight.  I believe that the rear of the frame is a beautiful thing when one has the ability to "open it up."  Remove the side covers, battery box, relocate the oil tank and battery, and leave a big gapping hole back there.  I like that.   ...I am not certain that the discussion needs to keep dancing around this idea of saving weight; the loss of a few pounds here and there really cannot be discerned on out little baby elephants, though I agree that the idea of saving weight on a "race" bike is generally though of as the more noble pursuit.

All that said, I am convinced that we should be talking about removing the battery in terms of aesthetics before weight gains/loss.  Do it because it looks bloody fabulous.

The next time your girlfriend/wife is in a rush tell her, “you might already be there if you just lost some wait,” and see what she says.  Of course she will not hear “wait,' but “weight.”  On a later occasion tell her, “baby, you are so beautiful, nobody will be thinking about the time when you arrive.”  I hope that makes my point?  No?  Well, it would be a silly thing to do anyway.

By the way, the bike looks great.  Where was that picture taken?
Peace and grease

-fang

[Bodi]

Most race bikes I've worked on (dirt track singles / twins, not 4 cyl street race bikes) use a little black box ignition unit and a small NiCd battery that will run the bike for maybe an hour.
For any street bike with lights you need an alternator and the SOHC4 alternators need a battery to "start" the field coil.
In theory you could add a small permanent magnet in the field coil structure and have it self-start, if the magnet was big enough to make enough power for the system to get going but small enough to produce less power than the ignition needs then the stock regulator would still be useable too.
A samarium-cobalt magnet has very high magnetism and can survive up to around 300°C so it should be OK in the alternator.
You could also make a permanent magnet rotor and lose the field coil completely, or make a permanent magnet field piece. The permanent rotor could give much more power output than the induced field system and weigh a lot less... hmmm. You would need a completely different regulator system too though.

[csendker]

I'm only loosly following the concept of battery removal because I have no interest in removing mine.  Hell, if I could find an industrial strength one I slap it in.  That said, virtually all of the previous discussions have indicated 'wait' loss in one way or another.

All that said, I am convinced that we should be talking about removing the battery in terms of aesthetics before weight gains/loss.  Do it because it looks bloody fabulous.

But now that you have brought this up, damn, lassarde's bike does look nice, particularily with that big hole there.

[lessarde]

Hello, the picture was taken just outside Steamboat, CO.  I live just down the road and we went camping up there last weekend.  I have several buddies who also have cafe style bikes and we did a riding/camping excursion.  This is the third cafe'd CB750 I've done and each one gets another nuance.  It's pretty fun and my buddy and I have started building them to sell, mainly just to pay for the project bikes we have.   

[SteveD CB500F]

I have tried the bat-pac and it definately does not work. 

I have removed the link from the FAQ.  Sorry if I've mislead anyone but if you read their site it is quite clear that the product will not work with systems that require and energised alternator.

Most of the links in the FAQs have been in there from day 1 (or 2 anyway...) and this one must have been recommended by a member somewhere.

[78CB750F1]

Your cafe conversion looks great - where did you relocate the oil tank to?

[lessarde]

Thanks, the oil tank is just pushed up behind the air filters.  I'm working with a welder friend of mine on a better, more stealthy tank right now that should be almost completely hidden.

[Dennis]

In theory you could add a small permanent magnet .....
You could also make a permanent magnet rotor and lose the field coil completely, .....
 The permanent rotor could give much more power output than the induced field system and weigh a lot less... hmmm. You would need a completely different regulator system too though.

This is intresting if anyone knows how to make the PM rotors. Rewiring for the regulator is pretty simple and straight forward as you probably already know.

[cd811]

I think on this subject ,my experience is worthy...when I first built my my bike I started with a 4 amp battery...small and cool...but it would NOT last(minimal wires,points, ss rec/reg)...it needed charging at least once a month...so I went to a 8 amp battery and have had no problem...basically, the sohc750 charging system, huh...sucks...and it needs battery amps to work right....period

[Pinhead]

Could we possibly use the permanent magnent rotor off a 550 or the likes? I've got a 650 and the rotor is problematic to say the least...